WTC and CTC - What is income?

My client is an owner manager of a close company. He has a favourable loan account balance with the company (money invested last year) and will choose to draw no salary next year - his regular income to be replaced by the loan repayment.

Does this mean that his income for tax credit purposes is nil and therefore a claim for WTC and CTC is acceptable?

I accept that there are potentially moral issues, but it seems to be a legitimate case for a claim. Afterall, true earned income is nil - the only income is a debt repayment.